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Yeah I know grumpy Mike. I took a look at your link and Google's a lot of things. I need a transistor which I have. I study them for a few hours. What I don't understand is, is the emittor what goes to the relay on the transistor? Since applied voltage to the base will draw current through the collector and send it out the emittor. Or do I have it backwards.

 Sorry but I do not understand your answer as to which line the diode goes on. I know the flow of electricity flow to the cathode and never against it. But when you say on the coil, do you mean, the cathode on the positive side of the coil and the anode to the transistor?
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is the emittor what goes to the relay on the transistor?
No it is the collector the emitter goes to ground.

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Since applied voltage to the base will draw current through the collector and send it out the emittor.
Yes an applied voltage to the base (through a resistor) will put a current through the base to the emitter and this will cause a current to flow from the collector to the emitter.

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Sorry but I do not understand your answer as to which line the diode goes on.
It is shown in the link you said you looked at. The anode goes to the collector (just like one end of the coil) and the cathode goes to the + supply driving the relay (just like the other end of the coil).
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where am i placing the transistor? I attached the circuit schematic.  


* mcu2.png (59.24 KB, 1079x615 - viewed 14 times.)
« Last Edit: February 10, 2012, 08:57:15 pm by annonymous » Logged

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I assume it should look like this --->


* mcu3.png (60.3 KB, 1080x616 - viewed 20 times.)
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Will you PLEASE look at the link I sent.
R2 should be direct to the arduino pin. The diode should be on the collector and other end of the coil. The other end of the coil, the one not connected to the collector should go with the diode to the relay power source.
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